Depends on what you wanna do. For me, I must have Bloons, Starbucks, ring video doorbell email and calendaring, Waze, Audible (for those hour plus commutes), and twitter
Baconit, Newsflow, if you're into sports SofaScore, Microsoft To-Do, myTube is what I use for browsing YouTube but there are several excellent third party apps for YouTube. And Enpass if you have lots of passwords to remember.
For me, "Money Wallet" is a must have. I've been using it for the past 5 years or so and it is probably the only thing keeping me tied to Windows 10 Mobile right now.
Developer says he has plans for a web version... if that comes out and i can use the app on any web browser then more than likely.. i'm gone lol.